When attempting to allocate fair values to assets upon acquisition of an enterprise, there is always a challenge when dealing with residual amounts to intangible assets, especially in distinguishing between those with finite lives as opposed to infinite ones. One argument I have encountered in several circumstances is how much of a valuation one can attach to an enterprise's workforce in contributing to enterprise value. Most of those instances have tended to be based on false assumptions, as a workforce can fundamentally change after a takeover, whether through turnover, planned reductions by the acquirer, or just overly optimistic estimations of the workforce's capabilities.
As far as financial reporting is concerned, IFRS has mostly ruled out such allocations to intangible assets of finite lives. IFRS 3 explicitly states that it is not an identifiable asset (at par. B37). In addition, IAS 38 points out that there is insufficient control over the economic benefits that may result from the assembled workforce (at par. 15). However, there are several identifiable assets that can arise in that area, such as non-competition agreements or employment contracts that are determined to be below-market from the employer's perspective. These, and especially the latter, would be quite sensitive information, in which the detail would be best kept locked away in the acquirer's files!
A valuation may still be relevant in determining allocations to intangible assets that are allowed to be recognized, such as a relationship with a key customer. In such an instance, it is seen as a contributory asset, a relevant part of which is there to sustain the relationship. The best method for determining its value is seen to be that of "reproduction cost" (as opposed to "replacement cost"), which would include the cost of recruiting, training and allowing for attaining maximum effectiveness after going through the appropriate learning curves. This is a component of what is known as the "multi-period excess earnings method," which is a fallback calculation when a more direct estimation of economic benefits is not possible. This is quite an arcane area which has still not been fully discussed in the professional literature, and I have never seen it being properly calculated in practice by others.
That is a summary explanation of the quantitative considerations involved in this matter. There is also the qualitative side, which is often given short shrift in M&A discussions. However, many acquisitions have failed spectacularly, because the acquirer failed to take note of what was happening under the surface at its target.
The corporate cultures of both parties, and potential clashes, is a particularly well-known area for potential downfalls. A target's corporate history, however, may be of more relevant interest. For example, the skills needed to handle startups are not necessary appropriate when the enterprise becomes more mature, and an owner-entrepreneur's behaviour is quite different from that of a professional manager. As well, personal relationships—on many levels, both inside and outside the enterprise—may influence future outcomes, both before and after an acquisition takes place, and those tend to be insufficiently documented. It may well be in an acquirer's best interest to buy some drinks at the bar for some of the key parties (not necessarily at the top levels) or third parties and have a wide-ranging chat with them, before any approaches are being considered. That would be money well spent, before intentions are actually expressed, non-disclosure agreements are signed, and people start feeling committed toward achieving an outcome that would not eventually be beneficial to the acquirer. Of course, there are some crucial legal aspects that are also involved in this entire process, so it might be a good idea to discuss your proposed tactics with a lawyer with great M&A experience before going ahead.